feat: render per-vertex color triangle

- Add shader class for vertex/fragment program compilation
- Add vao class for vertex array object management
- Render RGB gradient triangle with interpolated vertex colors

cbt/opengl/shader.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <string>
+
+#include "glad/glad.h"
+
+namespace cbt::opengl {
+
+class shader {
+    GLuint m_id = 0;
+
+public:
+    shader();
+    ~shader();
+
+    shader(const shader&) = delete;
+    shader& operator=(const shader&) = delete;
+
+    shader(shader&& other) noexcept;
+    shader& operator=(shader&& other) noexcept;
+
+    auto compile_vertex(const char* source) -> bool;
+    auto compile_fragment(const char* source) -> bool;
+    auto link() -> bool;
+    auto use() const -> void;
+    auto unuse() const -> void;
+    auto id() const -> GLuint;
+    auto valid() const -> bool;
+};
+
+}